align reference image with orthographic camera
Rotation values should be [54,736; 0; 45]

The provided picture is showing an Isometric Graphic.

In this particular case, by measuring the ratio between the edges,




and the projected angles of what we can imagine as perpendicular extrusion (the bridges) of a quadrangular face, we can deduce that we are in front of an Isometric axonometry with 120°, 120° 120° angle between axis.

But as I marked in bold, 60° is the projected angle, that means that is the result of the transformation of the camera and should be not used straightfoward as input for the X rotation.

Relying instead on the the math that's describing the camera orientation for such type of projection, we discover that the real X rotation is give by the formula:

X rotation = 90°-arctan(sin 45°) = 90°-35,264°= 54,736°